In a rotary offset printing press, a plate cylinder is disposed in rolling engagement with a blanket cylinder, which in turn contacts the web (the material to be printed upon). In the course of a print run, it is often necessary from time to time to adjust the position of the plate cylinder relative to the blanket cylinder. For example, an adjustment might be necessary so that the image being printed registers (matches) properly with an image already on the web. The register may need adjustment laterally (in the direction of the cylinder axes) or circumferentially (rotationally). Such adjustment might be necessary, for example, in a typical color printing press having four print units, each print unit printing dots of unique color. The combination of these colored dots on the paper creates a colored image. Each set of colored dots must be printed in alignment with the others in order to produce a sharp colored picture. If the dots are printing out of alignment, it is necessary to adjust the register of the print units so that they print their dots in proper alignment.
Apparatuses that adjust the lateral and circumferential position of the print cylinder are known to the art. In some of these apparatuses, the lateral positioner and the circumferential positioner are on opposite sides of the printing press. However, because the positioners are on opposite sides of the printing press, it is difficult for the press operator to make repeated adjustments of the cylinder position.
In other positioning apparatuses, this problem is solved by placing the lateral and circumferential positioners on the same side of the press. These apparatuses are easier to operate and take up less space, but they are complex and, thus, expensive.